Carbonaceous materials are well known and are useful as supports for various catalytic metals. When used as a support these carbonaceous supports are usually in the shape of spheres, plates, pellets, rods, fibers, with spheres being preferred. For example, U.S. Pat. No. 4,471,072 discloses a process for preparing a carbonaceous pyropolymer on a solid support. That is, a carbonaceous material is deposited on a solid support and takes the shape of the solid support.
Further, U.S. Pat. No. 4,329,260 discloses a carbonaceous composition which is prepared by pyrolyzing a hydrocarbon onto a solid support followed by leaching of the support. The composition is identified as a shaped replication support and is stated to have an Apparent Bulk Density (ABD) of about 25 to about 100% of the support and a crush strength of about 0.5 to about 14 kg.
Finally, U.S. Pat. No. 4,499,201 discloses a process for removing the alumina substrate from a carbonaceous pyropolymer which has been deposited on the substrate. This process uses a chloride containing compound at elevated temperatures to remove the alumina substrate.
Applicants have prepared a carbonaceous support which differs from the carbonaceous materials disclosed in the prior art. The instant composition is characterized in that substantially all of its pores have diameters that are less than about 300 .ANG.. The pore size distribution is described by a bi-modal distribution curve, i.e., a curve having two distinct maxima, in which the maxima occur at average diameters of about 60 to 90 .ANG. and about 120 to 160 .ANG.. These compositions also have a crush strength of at least 6 kg.
The carbonaceous pyropolymer compositions of this invention are prepared by pyrolyzing a hydrocarbon such as toluene onto a substrate such as spherical alumina. Next the alumina is leached away using an acid such as sulfuric acid. Finally, at least one more layer of carbonaceous pyropolymer is deposited onto the leached carbonaceous composition by pyrolyzing a hydrocarbon onto the leached composition to give the finished carbonaceous composition.